Sliders bonded by a debondable encapsulant comprising different polymers formed via in situ polymerization

ABSTRACT

A slider assembly is provided comprising a plurality of sliders bonded by a debondable solid encapsulant comprised of different first and second polymers The solid encapsulant is comprised of a polymer prepared by polymerizing an encapsulant fluid comprising a homogeneous mixture of first and second constituents. The first constituent is comprised of a first monomer suitable for in situ polymerization to form the first polymer. The second constituent is comprised of the second polymer or a second monomer suitable for in situ polymerization to form the second polymer. The first constituent does not substantially react with the second constituent. Each slider has a surface that is free from the encapsulant. The encapsulant-free surfaces are coplanar to each other. Also provided are methods for forming the assembly and methods for patterning a slider surface using the encapsulant.

TECHNICAL FIELD

The invention relates generally to the bonding of one or more sliders ina polymeric encapsulant. More particularly, the invention relates toplanarized slider assemblies bonded by a debondable polymericencapsulant comprised of different polymers formed via in situpolymerization of an encapsulant fluid. The invention also relates tomethods that use such encapsulants in conjunction with resists toproduce magnetic head sliders having patterned air-bearing surfaces.

BACKGROUND

A magnetic storage system typically includes one or more magneticrecording disks having surfaces from which data may be read and to whichdata may be written by a read/write transducer or “head.” The transduceris supported by an air-bearing slider that has a top surface attached toan actuator assembly via a suspension, and a bottom surface having anair-bearing design of a desired configuration to provide favorableflying height characteristics. As a disk begins to rotate, air entersthe leading edge of the slider and flows in the direction of thetrailing edge of the slider. The flow of air generates a positivepressure on the air-bearing surface of the slider to lift the sliderabove the recording surface. As the spindle motor reaches the operatingRPM, the slider is maintained at a nominal flying height over therecording surface by a cushion of air. Then, as the spindle motor spinsdown, the flying height of the slider drops.

The manner in which a slider is manufactured can affect flying height.Preferably, variations in the physical characteristics of the slider,e.g., those due to manufacturing tolerances, should not substantiallyalter the flying height of the slider. If this result is not achieved,the slider's nominal flying height must be increased to compensate forvariations between sliders.

A number of technologies may be employed to pattern such slidersurfaces. For example, mechanical processes such as cutting or abradinghave been proposed to remove material from a slider surface. Similarly,non-mechanical processes such as laser ablation, in which high intensitylight is used to evaporate material from sliders, have also beenproposed. Alternatively, material may be added to slider surfaces toalter their configuration to provide favorable flying heightcharacteristics. In some instances, these technologies have been used inconjunction with photolithographic and other semiconductor processingtechniques. In addition, these technologies may be adapted to pattern aplurality of air-bearing slider surfaces simultaneously and/orsystematically.

Thus, several approaches have been developed to facilitate the handlingof a plurality of sliders for simultaneous and/or systematic patterningof their air-bearing surfaces. For example, U.S. Pat. No. 5,932,113 toKurdi et al. describes a method for preparing the air-bearing surface ofa slider for etch patterning. The method involves applying first andsecond thin films comprising, respectively, first and second air-bearingsurfaces, to a carrier in a manner such that the first and second thinfilm are separated by a recess. An adhesive film is applied over thefirst and second thin films adjacent to the first and second air-bearingsurfaces. Then, a curable acrylate adhesive fluid is deposited in therecess and held therein by the adhesive film. Once the fluid is cured,the adhesive film is removed. The resulting slider assembly may then bepatterned by etching. For example, the first and second air-bearingsurfaces may be coated with an etch mask, which is then developed toallow for the patterning of the first and second air-bearing surfaces.U.S. Pat. No. 6,106,736 to LeVan et al. describes a similar method ofpreparing an air-bearing surface of a slider for etch patterning, exceptthat a heated wax is employed in place of the curable acrylate adhesive.

In sum, the above-described approaches employ an encapsulant to fill thegaps between sliders to protect the edges of the sliders duringpatterning. However, these encapsulants suffer from a number ofdisadvantages. For example, the curable encapsulants described in Kurdiet al. and the waxes described in LeVan et al. often exhibit unfavorablebonding and/or debonding performance. In particular, cured epoxymaterials, e.g., pure thermosetting epoxy resins, can be removed fromsliders only with great difficulty and often leave significant materialresidue on the slider surfaces. In addition, the prior art encapsulantssuffer from incompatibility with solvents that are used with thephotolithographic techniques for patterning air-bearing surfaces. Thatis, the prior art encapsulants are mechanically unstable and are subjectto solvation when exposed to fluids used in photolithographictechniques.

Recently, advances have been made with respect to slider assembliescomprising a plurality of sliders bonded by a solid debondable polymericencapsulant. For example, silicon-containing polymeric encapsultants forforming slider assemblies are described in U.S. patent application Ser.No. 10/611,418, entitled “Sliders Bonded by a Debondable Silicon-BasedEncapsulant,” inventors McKean et al., filed on Jun. 30, 2003.Additional encapsulant technologies are described in U.S. patentapplication Ser. No. 10/611,673, entitled “Sliders Bonded by aDebondable Encapsulant Containing Styrene and Butadiene Polymers,”inventors Miller et al. filed on Jun. 30, 2003, in U.S. patentapplication Ser. No. 10/611,317, entitled “Sliders Bonded by aDebondable Encapsulant Containing Styrene and Acrylate Polymers,”inventors McKean et al., filed on Jun. 30, 2003, U.S. patent applicationSer. No. 10/672,011, entitled “Sliders Bonded by a DebondableNon-Stoichiometric Encapsulant,” inventors Buchan et al. filed on Sep.25, 2003, and U.S. patent application Ser. No. 10/673,052, entitled “AStable Encapsulant Fluid Capable of Undergoing Reversible Diels-AlderPolymerization,” inventors Brock et al. filed on Sep. 26, 2003.

Nevertheless, there exist opportunities in the art to providealternatives to known encapsulants for forming slider assemblies. Inparticular, it has been discovered that an improved polymericencapsulant comprised of a plurality of polymers may be prepared by insitu polymerization of an encapsulant fluid containing a homogeneousmixture of constituents. Such encapsulants may for an interpenetratingpolymeric network that allows for improved debondability.

SUMMARY OF THE INVENTION

Accordingly, one aspect of the invention relates to a slider assemblyformed using a debondable solid encapsulant.

Another aspect of the invention pertains to a method for forming suchslider assemblies.

Yet another aspect of the invention provides methods for using adebondable solid encapsulant to pattern an air-bearing surface of aslider.

Additional aspects, advantages and novel features of the invention willbe set forth in part in the description that follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing, or may be learned by practice of the invention throughroutine experimentation.

In a first embodiment, the invention provides a slider assemblycomprising a plurality of sliders bonded by a solid debondableencapsulant. Each slider has an encapsulant-free surface, and theencapsulant-free surfaces are coplanar to each other. The encapsulant iscomprised of different first and second polymers and is formed via insitu polymerization of an encapsulant fluid. The encapsulant fluid iscomprised of a homogeneous mixture of first and second constituents. Thefirst constituent is comprised of a first monomer suitable for in situpolymerization to form the first polymer. The second constituent iscomprised of the second polymer or a second monomer suitable for in situpolymerization to form the second polymer. The first constituent doesnot substantially react with the second constituent.

A variety of chemistries may be used. For example, the first constituentis comprised of an amine, e.g., a tetraamine, and an epoxide, e.g., adiepoxide, optionally in a stoichiometric ratio. In addition, the firstmonomer may be comprised of an acrylate. In some instances, the firstpolymer is a thermosetting polymer and the second polymer is athermoplastic polymer. When the second constituent is comprised of thesecond monomer suitable for in situ polymerization, the first and secondpolymers may be polymerized via different mechanisms. For example, thefirst polymer may be polymerized via condensation, e.g., reactionbetween an amine and an epoxide, and the second polymer may bepolymerized via addition, e.g., addition polymerization of an acrylate.

In addition, different types of polymeric structures may be employed.For example, the first polymer may be comprised of a linear polymer, abranch polymer, or a network polymer. The second polymer may becomprised of a linear polymer. In some embodiments, the encapsulant istransparent.

Typically, the slider assembly is used as an intermediate to patternair-bearing slider surfaces. Thus, the assembly may have a contiguousplanar surface comprised of at least one encapsulant region andcontaining the coplanar slider surfaces. In addition, the sliders may bearranged in an array, e.g., a rectilinear array, such that they do notcontact each other. Often, the coplanar surfaces of the sliders are eachan air-bearing surface in contact with a substrate. Such a substrate maybe comprised of a laminate of a flexible tape and an adhesive. Forexample, the adhesive may be a pressure sensitive adhesive thatpreferentially adheres to the tape over the air-bearing surfaces. Forease in handling, a carrier may be attached to the encapsulant, at leastone slider, or both, without covering any of the coplanar slidersurfaces.

In another embodiment, the invention provides a method for forming aslider assembly. A plurality of sliders, each having a surface, isarranged such that the surfaces are coplanar to each other. Theencapsulant fluid as described above is dispensed to bond the sliderswithout contacting the coplanar slider surfaces. Once dispensed, theencapsulant fluid is polymerized in situ to form a solid debondablepolymeric encapsulant comprised of the first and second polymers.

When both the first and second constituents are suitable for in situpolymerization, polymerization may take place simultaneously. Typically,polymerization is carried out in a temperature range of about 60° C. toabout 150° C. Optionally, the polymerization temperature range is ofabout 80° C. to about 120° C.

Preferably, the encapsulant fluid dispensed in step (b) does not containany solvent. To ensure proper gap filling capabilities, the fluidmixture may have an initial viscosity of no more than about 800centistokes. Optionally, the initial viscosity is no more than about 500centistokes.

In a further embodiment, the invention provides a method for patterningan air-bearing surface of a slider. A slider is provided such that aportion of the slider other than an air-bearing surface thereof isencapsulated in a debondable solid encapsulant as described above. Aresist layer is applied on an air-bearing surface of a slider, and aportion of the resist layer is removed to uncover a portion of theair-bearing surface in a patternwise manner. Material is adding materialand/or removing from the uncovered portion of the air-bearing surface.Notably, the encapsulant is mechanically stable upon exposure to anyfluid employed when the resist layer is applied, when the resist layeris removed, and/or when material is added to and/or removed from theair-bearing surface. As a result, the air-bearing surface of the slideris patterned. Typically, the resist layer is exposed to photons in apatternwise manner before a portion thereof is removed. Afterwards, theencapsulant may be removed via solvation by a solvent not found in theresist layer.

In a first embodiment, the present invention provides a slider assemblycomprising a plurality of sliders bonded by a solid encapsulant. Theencapsulant is comprised of a polymer prepared by polymerizing, e.g.,via in situ polymerization, a mixture of first and second monomers in anonstoichiometric ratio effective to render the encapsulant debondable.Each slider has a surface that is free from the encapsulant, and theencapsulant-free surfaces are coplanar to each other.

Typically, the slider assembly has a contiguous planar surface comprisedof at least one encapsulant region and containing the coplanar slidersurfaces. In addition, the sliders may be arranged in an array, e.g.,rectilinear array, such that the sliders do not contact each other. Thecoplanar surfaces of the sliders may be air-bearing surfaces.

Any of a number of monomers may be used in the practice of the inventionas long as the polymer is prepared from a stoichiometric excess of theone of the monomers to the other monomer. For example, the polymer maybe prepared with an excess of an amine-containing monomer, or an excessof an epoxide-containing monomer. Typically, at least one of themonomers has a structure suitable for forming a linear polymer, abranched polymer, or a polymeric network.

In another embodiment, the invention provides a method for forming aslider assembly. The method involves arrange a plurality of sliders eachhaving a surface such that the surfaces are coplanar to each other. Afluid mixture of first and second monomers in a nonstoichiometric ratiois dispensed in a manner effective to bond the sliders withoutcontacting the coplanar slider surfaces, and the first and secondmonomers are polymerized to form a polymeric debondable solidencapsulant.

In a related embodiment, the invention provides a method for forming aslider assembly that involves first selecting first and second monomerssuch that polymerization thereof in a stoichiometric ratio forms anondebondable solid encapsulant. Then a fluid mixture of the first andsecond monomers is produced in a nonstoichiometric ratio. The mixture isdispensed in a manner effective to bond a plurality of sliders. Oncedispensed, the first and second monomers are polymerized to form adebondable solid encapsulant.

Typically, sliders are arranged on a laminate of a flexible tape and anadhesive such that the slider surfaces contact the adhesive. In such acase, the adhesive is preferably resistant and optimally impervious tosolvation by the fluid mixture. To facilitate intimate bonding betweenthe sliders, the fluid mixture may have an initial viscosity of no morethan about 800 centistokes.

In a further embodiment, the invention provides a method for patterningan air-bearing surface of a slider. A resist layer is applied on anair-bearing surface of a slider such that at least a portion of theslider other than the air-bearing surface is encapsulated in adebondable solid encapsulant. The encapsulant is comprised of a polymerprepared by polymerizing a mixture of first and second monomers in anonstoichiometric ratio effective to render the encapsulant debondable.A portion of the resist layer is removed to uncover a portion of theair-bearing surface in a patternwise manner. Material may be added to,or more typically, removed from the uncovered portion of the air-bearingsurface. As a result, the air-bearing surface of the slider ispatterned. The encapsulant is mechanically stable upon exposure to anyfluid employed to effect patterning of the air-bearing surface.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically illustrates a prior art slider having roundedcorners and edges.

FIGS. 2A–2F, collectively referred to as FIG. 2, depict an example ofthe inventive slider assembly as well as a method for forming theassembly. FIGS. 2A and 2B depict the arrangement of sliders in arectilinear array on a substrate in the form of a tape having apressure-sensitive adhesive coated on an upper surface thereof in topview. FIG. 2B depicts the arrangement of sliders of FIG. 2A incross-sectional view along dotted line A. FIGS. 2C and 2D depict theformation of an encapsulated array in top and cross-sectional views,respectively. FIGS. 2E and 2F depict the encapsulated array of FIGS. 2Cand 2D attached to a carrier and having the tape removed in top andcross-sectional views, respectively.

FIGS. 3A–3E, collectively referred to as FIG. 3, depict an example of amethod for photolithographically patterning an air-bearing surface of aplurality of sliders provided in the form of the slider assemblydepicted in FIG. 2. FIG. 3A depicts in cross-sectional view theapplication of a photoresist layer on the air-bearing surface of theslider assembly. FIG. 3B depicts in cross-sectional view the patternwiseexposure of the photoresist layer. FIG. 3C depicts in cross-sectionalview the removal of the resist layer according to the pattern formed inFIG. 3B. FIG. 3D depicts in cross-sectional view the removal of materialfrom the exposed slider surfaces. FIG. 3E depicts in top view debondedsliders having patterned air-bearing surfaces.

DETAILED DESCRIPTION OF THE INVENTION

Definitions and Overview

Before describing the present invention in detail, it is to beunderstood that this invention is not limited to processing conditions,manufacturing equipment, or the like, as such may vary. It is also to beunderstood that the terminology used herein is for describing particularembodiments only and is not intended to be limiting.

It must be noted that, as used in the specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a resist layer” includes a single resist layer as well asa plurality of resist layers, reference to “a slider” includes a singleslider as well as a plurality of sliders, and the like.

In describing and claiming the present invention, the followingterminology is used in accordance with the definitions set out below.

The term “array” as used herein refers to a two-dimensional arrangementof items such as an arrangement of sliders. Arrays are generallycomprised of regular, ordered items as in, for example, a rectilineargrid, parallel stripes, spirals, and the like, but non-ordered arraysmay be advantageously used as well. In particular, the term “rectilineararray” as used herein refers to an array that has rows and columns ofitems wherein the rows and columns typically, but not necessarily,intersect each other at a ninety-degree angle. An array is distinguishedfrom the more general term “pattern” in that patterns do not necessarilycontain regular and ordered features.

The term “bond” is used herein in its ordinary sense and means to joinsecurely. Typically, but not necessarily, “bonding” is achieved throughadhesive forces. Similarly, the term “debondable” as in “debondableencapsulant” refers to an encapsulant that is susceptible to completeremoval from the surfaces of items bonded thereby without damage to theitems.

The term “encapsulant” refers to a material suited to bond a pluralityof items or to encase one or more items in a confined space. Typically,an “encapsulant” is a solid material formed from an “encapsulant fluid”that has been subjected to conditions effective for solidification tooccur. For example, an “encapsulant” may be formed from thepolymerization of an “encapsulant fluid” comprising a mixture of firstand second monomers.

The term “fluid” is generally used in its ordinary sense and refers tomatter that is capable of flow. Typically, but not necessarily, a fluidcontains a liquid and optionally a solid or a gas that is minimally,partially, or fully solvated, dispersed, or suspended in the liquid. Forexample, a fluid may be aqueous or nonaqueous in nature and may containorganic solvents and the like having polymers and/or monomers solvatedtherein.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.

The term “polymer” is used herein in its conventional sense to refer toa compound having two or more monomer units, and is intended toencompass homopolymers as well as copolymers, including, for example,graft copolymers. The term encompasses polymers of all types and is notlimited to linear, branched, cyclic, or crosslinked polymers. Thus, theterm “polymerization” refers to processes in which monomers cometogether to form a polymer. As used herein, the term is meant toencompass “crosslinking” processes in which network polymers may beformed.

The terms “stoichiometry” and “stoichiometric” are used herein in theirordinary sense and refer to the quantitative relationship betweenreactants and products in a chemical reaction. Thus, the term“nonstoichiometric” as used herein refers to a chemical reaction betweena plurality of reactants that takes place with an excess or deficiencyof at least one reactant. For example, amine groups will react with anequal number of epoxide groups in a stoichiometric reaction. That is,the stoichiometric ratio of amine groups and epoxide groups for such areaction is 1. Thus, when the same number of amine groups and epoxidegroups is provided for reaction, the reaction that takes place isconsidered “stoichiometric.” It follows, then, when an excess of aminegroups or epoxide groups are provided for reaction, the reaction thattakes place is considered “non-stoichiometric.” Similarly, a reactionthat takes place between equal quanitities of a first reactantcontaining X amine groups and a second reactant containing Y epoxidegroups is considered “non-stoichiometric” when X does not equal Y.

The term “solid” is used in its ordinary sense and refers to items thathave definite shape and volume.

The term “substantially” as in, for example, the phrase “substantiallyidentical in geometric dimensions” refers to items having dimensionsthat do not deviate from each other by more than about 10%. Preferably,the difference in the dimensions is no more than 1%. Optimally thedifference is no more than 0.1%. Other uses of the term “substantially”involve an analogous definition.

Slider Assembly

Generally, the invention relates to the patterning of an air-bearingsurface of a slider, and various embodiments of the invention provideslider assemblies suitable for use in conjunction with such surfacepatterning processes. In particular, the invention provides anencapsulant fluid comprised of a homogeneous mixture of constituents.The encapsulant fluid is used to forming a debondable encapsulantcomprised of a plurality of different polymers to encapsulate one ormore sliders. At least one of the constituents is comprised of a monomersuitable for in situ polymerization.

For example, the encapsulant may be formed via concurrent polymerizationof a homogeneous mixture of different types of monomers in the same“pot.” Each monomer type may undergo a different polymerizationchemistry to form different polymers. The chemistries may be selected tooccur over the same temperature ranges and not substantially affect eachother. In addition, the mixture may exhibit low viscosity to result in ahomogeneous, transparent encapsulant with the requisite dimensionaltolerances, dimensional stability, and solvent resistance. Theencapsulant may be solvated or may undergo debonding via by applicationof an appropriate solvent.

In order to elucidate the invention fully, FIG. 1 depicts a knownslider. As with all figures referenced herein, in which like parts arereferenced by like numerals, FIG. 1 is not to scale, and certaindimensions may be exaggerated for clarity of presentation. A slider 100having a generally rectangular air-bearing surface is depicted inFIG. 1. Located on the air-bearing surface of slider 100 are leadingpads 101 and 102 disposed on a first shallow step region 110.Additionally, the slider 100 includes a trailing pad 103 disposed on asecond shallow step region 111. The shallow step regions 110 and 111 areapproximately the same depth with respect to the air-bearing surface.

The shallow step region 110 extends along the leading edge 140 of slider100 and has side rails that extend along the side edges 150 and 151 ofslider 100. The shallow step regions 110 and 111 provide the positivepressure regions of slider 100. More specifically, the shallow stepregion 110 pressurizes leading pads 101 and 102 and shallow step region111 pressurizes trailing pad 103 during operation, to give slider 100 apositive lift. Pressurization mainly occurs at the step transitionbetween the shallow step regions and the air-bearing pads. The negativepressure region 120 is responsible for pulling slider 100 towards thedisk surface during operation. During operation, the disk is rotatingand the slider is flying above the disk surface. In general, thenegative and positive pressure regions of slider 100 are counterbalancedto provide a relatively flat flying height profile.

It should be evident from the slider depicted in FIG. 1 that the stepson the air-bearing surface are patterned with sufficient precision toprovide a desired flying height profile. Although the size of thesliders may vary, recent advances in slider processing technology allowfor the production of sliders having a rectangular air-bearing surfacearea on the order of 1 mm² or less. Accordingly, there is an increasingdemand for technologies that effect precise control over the placementand spatial orientation of slider surfaces when the surface ispatterned.

To this end, the invention provides a slider assembly comprising aplurality of sliders. The sliders are bonded by a debondable solidencapsulant. Depending on the processing techniques that may be used inconjunction with the assembly, certain bonding materials areparticularly suitable for use as encapsulants. Selection criteria forsuitable encapsulant are discussed below.

The invention may be employed using sliders composed of any materialsuitable for use as a slider having appropriate thermal, electrical,magnetic and mechanical properties. Typically, sliders for magneticheads are made from a hard material having a high modulus of elasticity.Such materials include ceramics such as carbides, nitrides, and oxides.Carbides such as aluminum carbide, silicon carbide, titanium carbide,boron carbide, geranium carbide, tungsten carbide, and mixed-metalcarbides (e.g., AlTiC or Al₂O₃TiC) are generally preferred but othermaterials such as titanium oxide, silicon nitride and silicon may beused as well. In addition, it is preferred that the slider is sized torequire only minimal material addition or removal in order to patternthe air-bearing surface.

Thus, sliders may be formed by first cutting a monolithic solid memberinto the plurality of sliders. The monolithic solid member may be grownor prepared in bulk, and depending on desired properties, the materialmay have a single crystalline, multicrystalline, or amorphousmicrostructure. Exemplary techniques for forming monolithic materialsinclude Czochralski, float zone and other methods known in the art.

Irrespective of the encapsulant employed to form the slider assembly,each slider of the assembly has a surface that is free from theencapsulant. These surfaces are coplanar to each other and typicallyrepresent air-bearing surfaces of the sliders. The coplanar arrangementof the slider surfaces is well suited for use in numeroussurface-patterning techniques such as those involving the use of maskingtechnology and/or the employment of photolithographic techniques. Insome instances, the slider assembly has a contiguous or a substantiallyplanar surface comprised of at least one encapsulant region andcontaining the coplanar slider surfaces. Such planar surface contiguityfacilitates the deposition of a uniform and/or contiguous film orcoating on the coplanar slider surfaces. Thus, any steps that may bepresent between an encapsulant region and the slider surfaces should beno more than that which would disrupt the deposition of a uniformcoating on the coplanar slider surface. Typically, such steps are nomore than about 5 micrometers in height to provide a high planarizationvalue.

In some instances, the slider has an additional planar surface opposingthe coplanar sliders surfaces. The additional planar surface may or maynot be contiguous and may be formed from the encapsulant and/or aslider. Such an additional planar surface may further facilitate ease inthe handling of the assembly.

In certain embodiments, the sliders of the assembly are substantiallyidentical in geometric dimensions. In addition, the sliders aretypically arranged in an array such that the distance between thesliders is minimized without having the sliders contact each other.Contact among the sliders increases the likelihood of slider damage.Often, rectilinear arrays are chosen to maximize the slider toencapsulant volumetric ratio.

The inventive slider assembly may be used as a convenient means forhandling and processing a plurality of sliders. To ensure that thesliders remain immobilized with respect to each other, the encapsulantmay be rigid. To provide acceptable rigidity, the glass transitiontemperature of the encapsulant, T_(g), is typically high, e.g., at leastabout 100° C. Encapsulants having a T_(g) of about 100° C. to about 140°C. are known in the art. In addition or in the alternative, the sliderassembly as described above may further include a carrier attached tothe encapsulant and/or at least one slider. The carrier is particularlyuseful when the encapsulant is brittle or otherwise difficult to handle.Usually, the carrier does not cover any of the coplanar slider surfaces.

The encapsulant may be selected for certain properties that willfacilitate its use in slider patterning techniques. While specificmaterials suitable for use as an encapsulant are discussed below,encapsulant materials generally share some common characteristics. As aninitial matter, the encapsulant should be able to bond with the slidersin a void-free manner without debonding until after the patterningprocesses have been completed. Because bonding behavior is often surfacedependent, the encapsulant should be selected according to the surfaceto which bonding is to take place. Particular attention should be paidto factors such as surface composition, morphology, and the like.

In addition, the encapsulant should be able to maintain its mechanicaland dimensional stability until debonding is desired. For example, theencapsulant preferably exhibits minimal or no shrinkage and/or swellinguntil debonding is desired. Furthermore, the encapsulant preferably isreadily debondable without damage to the sliders and without leaving anyresidue on the sliders. For example, the encapsulant may be debondedthrough washing in a solvent capable of solvating the encapsulant or acomponent thereof. In addition, or in the alterative, heat may beapplied to liquefy, vaporize, and/or discompose the encapsulant.

Thus, it should be evident that the encapsulant should be able towithstand the environmental conditions imposed on the sliders duringpatterning. For example, some slider patterning techniques require theexposure of sliders to a vacuum. Any outgassing from the encapsulant maycompromise the quality of the vacuum. Thus, it is sometimes preferredthat the encapsulant does not substantially outgas under vacuum. Asanother example, slider-patterning techniques may require thermalcycling of the sliders. Accordingly, it is preferred that theencapsulant be mechanically stable for thermal cycling, e.g., from about20° C. to about 100° C.

Method for Forming a Slider Assembly

The invention also provides a method for forming a slider assembly. Themethod involves arranging a plurality of sliders each having a surfacesuch that the surfaces are coplanar to each other. An encapsulant fluidis dispensed in a manner effective to bond the sliders withoutcontacting the coplanar slider surfaces. The dispensed encapsulant fluidis subjected to conditions effective for the fluid to form a debondablesolid encapsulant comprised of different first and second polymers fromthe encapsulant fluid. As discussed above, the encapsulant fluid iscomprised of a homogeneous mixture of first and second constituents asdescribed above. That is, the first constituent is comprised of a firstmonomer suitable for in situ polymerization to form the first polymer,and the second constituent is comprised of the second polymer orprecursor thereof.

Due to the precision required for forming the slider assembly and thesize associated with the sliders, manual slider placement is typicallyundesirable. Instead, automated and/or robotic means for positioning orarrange the sliders may be preferred. Selection of an appropriate meansfor positioning or arranging the sliders depends on the speed andaccuracy required. In some instances, the sliders may be placedsimultaneously. In other instances, the sliders may be successivelyplaced. One of ordinary skill in the art will recognize that positioningmeans, may be constructed from, for example, motors, levers, pulleys,gears, a combination thereof, or other electromechanical or mechanicalmeans.

In order to maintain the sliders in proper position and spatialorientation to allow for solidification of the encapsulant to occur, ameans for immobilizing the sliders may be employed. For example, thesliders may be arranged on a substrate surface and immobilized thereonthrough mechanical action (e.g., clips, centripetal force),electrostatic attraction, magnetic forces, or other known immobilizingmeans. In some embodiments, the sliders may be temporarily immobilizedon a substrate through the application or use of an adhesive on thesubstrate surface, e.g., pressure sensitive adhesives such as acrylics,natural rubbers, butyl rubbers, polyvinylethers, silicones, and mixturesthereof. As the performance of pressure adhesives may vary withtemperature, an adhesive may be selected to exhibit improved performanceat temperatures ranging from about 25° C. to 30° C. The pressure ofapplication may range from about 10 lbs/cm² to 50 lbs/cm² and preferablyis about 25 lbs/cm². To deter the adhesive from leaving residue on theslider, the adhesive should preferentially adhere to the substrate overthe air-bearing surfaces.

As discussed above, the encapsulant fluid is dispensed in a mannereffective to bond the sliders without contacting the coplanar slidersurfaces. Thus, when the substrate surface is planar, the air-bearingsurfaces of the sliders may be placed in contact with the substratesurface to ensure that the air-bearing surfaces remain coplanar as wellas to deter contact with the encapsulant fluid. Any adhesive used shouldbe resistant or impervious to solvation by the encapsulant fluid or acomponent thereof to deter wicking of the encapsulant fluid via theadhesive to contact the slider surfaces.

The substrate may be comprised of any material compatible with theencapsulant fluid. In addition, the substrate is preferably selectedfrom a material that is softer than the slider to avoid damaging anyslider surface that comes into contact therewith. In some instances, aflexible substrate may be used to facilitate its removal. For example,any number of polymeric films may be used such as those derived frommonomers including ethylene, propylene, butylene and, homopolymers andcopolymers of these olefins; vinyl monomers such as vinyl acetate, vinylchloride, vinylidene chloride, vinyl fluoride, acrylonitrile, methylmethacrylate and mixtures thereof; of ethylene with portions of one ormore unsaturated monomers such as vinyl acetate, acrylic acid andacrylic esters; as well as styrenes, carbonates, esters and urethanes.Polymers capable of withstanding relatively high temperatures, such aspolyimide may be a desirable substrate material when the substrate maybe exposed to a high temperature. Polyimides are commercially available,e.g., under the tradename Kaptong®, from DuPont (Wilmington, Del.).Thus, it should be apparent that the substrate may be a laminate of aflexible tape and an adhesive, wherein the adhesive is in contact withthe air-bearing surfaces. Exemplary adhesive thicknesses may range fromabout 2 to about 25 micrometers and the tape thickness may range fromabout 12 to about 150 micrometers.

The adhesive strength of the adhesive film varies from about 50 gm/20 mmup to about 100 gm/20 mm. Commercially available adhesive films includeV-8-S from Nitto Denko, which is a polyvinyl chloride based tape havinga 10 micrometer thick adhesive layer, a 70 micrometer thick polyvinylchloride flexible substrate and 100 g/20 mm of adhesion. Another film isthe Nitto Denko V-8-T, having the same composition as the V-8-S filmwith 50 gm/mm of adhesion.

Other useful films include Nitto Denko's BT-150E-EL film having 75 gm/20mm of adhesion, an ethylene vinyl acetate based tape having a 15micrometer thick adhesive layer; Lintec's Adwill P-1600 B film, which isa water flushable tape having a base material of polyolefin which is 110micrometers thick, an adhesive layer of polyacrylate which is 20micrometers thick and has adhesion of 140 gm/25 mm. In some instances,polyesters such as polyethylene terephthalate may be used as a tapematerial. For example, substrates comprised of a laminate of apolyethylene terephthalate tape having a thickness of about 37micrometers and an adhesive layer of about 5 micrometers are availablefrom 3M Corporation (St. Paul, Minn.).

As discussed above, the sliders are typically arranged in a rectilineararray on a planar substrate surface such that the distance between thesliders is minimized without having the sliders contact each other. As aresult, gaps or recesses are formed between the rows and columns. Thedistance between the rows and columns may range from about 50 to about1000 micrometers and can be as small as about 100 micrometers or less.The depth of the gaps depends upon the thicknesses of the sliders andmay range from about 100 to about 300 micrometers. While the encapsulantfluid may be dispensed in any manner effective to bond the sliderswithout contacting the coplanar slider surfaces, encapsulant fluidshould flow in certain ways to form certain embodiments of the sliderassembly. For example, in order to form void-free slider assemblies,encapsulant fluid is preferably injected or drawn into the gaps orrecesses between the rows and the columns. In addition, to form sliderassemblies having a contiguous planar surface comprised of at least oneencapsulant region and containing the coplanar slider surfaces, theencapsulant fluid preferably conforms to the slider surfaces and theplanar substrate surface to which the fluid comes into contact.Furthermore by bringing the level of encapsulant fluid to the same orhigher level as the sliders, an additional planar surface opposing thecoplanar sliders surfaces may be formed. Molds and equivalents thereofmay be advantageously used to confine encapsulant fluid flow.

The ability of the encapsulant fluid to gap-fill is dependent on anumber of factors. One particularly important factor is the viscosity ofthe encapsulant fluid. Viscosity is a measure of resistance of a fluidto sheer forces and is often roughly inversely proportional to thegap-filling ability of the fluid. Typically, the encapsulant fluid has alow initial viscosity, e.g., less than about 1000 centistokes.Preferably, the initial viscosity is no more than about 800 centistokes.More preferably, the initial viscosity is no more than about 500centistokes. For certain encapsulant fluids, an initial viscosity ofabout 20 to about 200 centistokes represents an optimal range forgap-filling ability. For encapsulant fluids that contain a solvent, ahigher solvent content tends to correlate with lower viscosity. In someinstances, an encapsulant fluid containing a polymer dissolved in asolvent exhibits a preferred viscosity at a solvent content of 30 wt %to about 50 wt %. An optimal viscosity may sometimes be found when thesolvent is present in a range of about 40 wt % to about 45 wt % of theencapsulation fluid.

Surface forces may also play a role in determining the ability of theencapsulant fluid to gap-fill. In general, the ability of an encapsulantfluid to fill a gap will depend, in part, on the affinity of the surfaceof the gap to the encapsulant fluid. Thus, proper selection of theencapsulant fluid according to the surface properties of the substrateand/or the sliders may enhance gap filling via capillary action.

Once proper distribution of the encapsulant fluid is achieved, thedispensed encapsulant fluid is subjected to conditions effective for thefluid to form a debondable solid encapsulant from the encapsulant fluid.Depending on the encapsulant used, solidification may take place via anumber of different mechanisms. For example, the in situ polymerizationreaction may be photoinitiated. In addition, when the encapsulationfluid contains a polymer dissolved in a solvent, formation of a solidencapsulant may involve removing the solvent. This may be achieved bysubjecting the encapsulation fluid to heat or reduced pressure.Nevertheless, solventless encapsulant fluids are generally preferredover encapsulant fluids.

In some instances, a combination of mechanisms may be employed. Forexample, a slider assembly may be formed in the manner as discussedabove wherein the encapsulation fluid is comprised of a polymerizableand/or crosslinkable monomer for forming the first polymer, a secondpolymer, and a solvent. Once dispensed, the solvent may be evaporated toform a debondable solid encapsulant comprising the first and secondpolymers, wherein the first polymer is prepared via in situpolymerization.

An example of the above-described method for forming the assembly isillustrated in FIG. 2. FIGS. 2A and 2B depict the placement of sliders10 in a four-by-four rectilinear array on a tape 12 having asubstantially planar upper surface 14. The upper surface 14 of the tapehas a coating of a pressure-sensitive adhesive 16 coated on an uppersurface thereof. Each slider has an air-bearing surface 18 and anopposing back surface 20. The air-bearing surfaces 18 are placed facingdownward to face the upper surface 14 of the tape and to contact thepressure sensitive adhesive 16.

Also provided is a rectangular frame 21 in contact with the pressuresensitive adhesive 16. Together with the frame 21, the tape 12 serves asa mold or container to confine the encapsulant fluid dispensed thereon.

FIGS. 2C and 2D depict the formation of an encapsulated array. Ingeneral, FIGS. 2C and 2D are identical to FIGS. 2A and 2B, except thatan encapsulant fluid 22 is dispensed on the tape 12 within the frame 21to a level that coincides with the exposed surface 20 of the sliders 10.As depicted in FIG. 2D, the encapsulant fluid conforms to the sides ofthe sliders 10 as well as the profile of the upper surface 14 of thetape. In addition, no wicking of the encapsulant fluid 22 is shownbetween air-bearing surfaces 18 of the sliders 10 and the adhesive 16.

As depicted in FIGS. 2E and 2F, once the encapsulant fluid 22 solidifiesto form the encapsulant 22S, the tape 12 may be removed to form theslider assembly 24. The slider assembly 24 has two opposing parallelplanar surfaces indicated at 26 and 28. Surface 26 is formed in part byair-bearing surfaces 18 of the sliders 10, while surface 28 is formed inpart by the back surfaces 20 of the sliders 10. A carrier 30 is attachedto surface 28.

Method for Patterning an Air-Bearing Surface of a Slider

The invention further provides a method for patterning an air-bearingsurface of a slider. The method involves applying a resist layer on anair-bearing surface of a slider, wherein at least a portion of theslider other than the air-bearing surface is encapsulated in a solidencapsulant comprising a polymer prepared by polymerizing a mixture offirst and second monomers in a non-stoichiometric ratio effective torender the encapsulant debondable. A portion of the resist layer isremoved to uncover a portion of the air-bearing surface in a patternwisemanner. In some instances, material is added to the uncovered portion ofthe air-bearing surface. In addition or in the alternative, material maybe removed from the uncovered portion of the air-bearing surface. As aresult, the air-bearing surface is patterned. Notably, the encapsulantis mechanically stable upon exposure to any fluid employed to apply theresist layer, to remove the resist layer, to add material to theair-bearing surface and/or to remove material from the air-bearingsurface.

In general, the resist layer may be applied using any of a number ofconventional techniques, e.g., sequential spin coating, casting,extruding or the like. For example, a resist composition may be providedin a liquid solvent on the substrate surface, and heated to remove thesolvent. As a result, the resist layer typically has a thickness ofabout 1 to about 20 micrometers, optionally about 2 to about 10micrometers. To effect controlled removal of portions of the resistlayer, it is preferred that the resist layer be applied with a uniformthickness.

To facilitate the patternwise removal of a portion of the resist layer,the resist layer may be comprised of a photosensitive composition thathas been exposed to photons in the patternwise manner. Photosensitivecompositions are typically polymeric and exhibit different removalproperties after exposure to electromagnetic radiation. For example,photosensitive compositions may exhibit increased mechanical integrityresulting from radiation-initiated crosslinking or decreased mechanicalintegrity resulting from radiation-initiated breakdown. Examples ofphotosensitive compositions include, but are not limited to, positiveand negative resists that are responsive to photon or electron beams.Positive photoresist compositions are more easily removed after exposureto radiation. Positive photoresists may include polymeric materials withweak links that degrade by the process of scission or contain aphotoactive component that renders the composition more soluble to asolvent upon irradiation. Negative photoresist compositions, on theother hand, become more difficult to remove after exposure to radiation.

Suitable photosensitive compositions such as photoresists may comprise,for example, poly(methyl methacrylate) (“PMMA”) or copolymers thereofsuch as poly(methyl methacrylate-co-t-butylmethacrylate), apoly(lactide) such as poly(lactide-co-glycolide), polymethacrylamide,polyoxymethylene, polyalkenesulfone, orpoly(glycidylmethacrylate-co-ethyl acrylate), epoxies, phenolics,polymers thereof, copolymers thereof, and combinations thereof.Photosensitive compositions may also contain photoactive compoundsincluding, but not limited to, diazonaphthoquinones, iodonium andsulfonium salts and o-nitrobenzyl esters.

Typically, the resist is irradiated using photonic radiation, e.g.,ultraviolet radiation and a mask to provide the desired pattern.Following exposure, the resist layer may be developed using a suitablesolvent to remove the irradiated or the non-irradiated areas to uncovera portion of each slider surface. One of ordinary skill in the art willrecognize that there are many commercially available photoresists havingdifferent exposure wavelengths, and that custom photoresist compositionsmay be formulated to have a particular exposure wavelength.

When one wishes to add material to the uncovered portion of theair-bearing surface, various techniques are known in the art ofsemiconductor fabrication. Exemplary techniques include, but are notlimited to, evaporation, sputtering, chemical vapor deposition, andelectroplating. Notably, deposition techniques must be chosen accordingto the material. For example, metals may be deposited by evaporation,sputtering, electroplating, chemical vapor deposition, etc.

In order to effect a high degree of control over the addition ofmaterial to the air-bearing surface, vacuum deposition technology isgenerally preferred. Such vacuum processes include, but are not limitedto, cathodic arc physical vapor deposition, electron-beam evaporation,enhanced arc physical vapor deposition, chemical vapor deposition,magnetronic sputtering, molecular beam epitaxy, combinations of suchtechniques and a variety of other techniques known to one of ordinaryskill in the art.

When one wishes to remove material from the air-bearing surface, anetchant may be used to effect chemical, mechanical and/or physicalremoval material. In some instances, an isotropic etchant may be used toremove material in a direction-invariant manner such that no differenceis exhibited in directional etching rate. Alternatively, an anisotropicetchant may be used to remove material preferentially in a particulardirection, e.g., according to crystallographic orientation of the solidbody or the direction of the light energy particles for light assistedetching. In some instances, an ionized gas such as argon-based orfluorine-based plasma or an ion beam may be used as an etchant. A liquidetchant may also be advantageously used as well.

Further information regarding patterning and etching processes usinglithographic techniques is provided in Sze (1983), “Lithography,” VSLITechnology, McGraw-Hill Book Company.

Thus, it should be apparent that encapsulant may be mechanically stableupon exposure to a variety of fluids employed to pattern the slidersurface. For example, any fluids associated with the application,development, and/or removal of a resist layer. Such fluids may compriseof organic and/or inorganic compounds and may be acidic, basic,oxidizing, or reducing in nature. In addition, aqueous and/or nonaqueousfluids may be used as well.

FIG. 3 depicts an example of the above-described method for patterningan air-bearing surface of a plurality of sliders provided in the form ofthe slider assembly depicted in FIG. 2. As shown in FIG. 3A, the sliderassembly 24 is placed on a flat surface such that the air-bearingsurface 28 of the assembly faces upward and the carrier 30 contacts theflat surface. A photoresist layer 32 is applied in a uniform thicknessover the air-bearing surface. Due to the planarization of air-bearingsurface 28, the resist layer may be applied as a thin, high-resolutioncoating. Planarized surfaces have been coated with resist layers havinga preferred thickness of about 1 to 25 micrometers and a more preferredthickness of about 2.0 to 15 micrometers. This provides a resolution ofabout 200 micrometers to 5 micrometers.

FIG. 3B depicts the patternwise exposure of the photoresist layer 32 tophotons. This is performed by providing a mask 34 having transparentregions 36 and opaque regions 38. A source 40 of photons is provided inorder to generate radiation, preferably substantially collimated, havinga wavelength to which the photoresist layer 32 is responsive. Typically,the wavelength is an ultraviolet wavelength. The mask 34 is placedbetween the photon source 40 and the photoresist layer 32 such that thetransparent regions 36 are in alignment with the air-bearing surfaces 18of the sliders 10. As a result, radiation is transmitted through thetransparent regions 36 of the mask 34, and the photoresist layer isconverted into a patterned layer comprising the exposed and theunexposed regions. In some instances, grayscale masks are employed.

FIG. 3C depicts the removal of a resist layer according to the patternformed in FIG. 3B. This is achieved by developing the exposed portionsof the photoresist layer 32 to facilitate removal thereof. In this case,the exposed portions are washed away with a solvent, leaving theunexposed portions intact. As a result, portions of the air-bearingsurfaces 18 are uncovered.

FIG. 3D depicts the removal of material from the uncovered slidersurfaces 18 by exposing the surfaces 18 to an etchant. By debonding theencapsulant 22S from the sliders, as depicted in FIG. 3E, encapsulantfree sliders 10, having patterned air-bearing surfaces 18, are formed.As discussed above, debonding may involve using a solvent to wash awaythe encapsulant or applying heat to liquefy, vaporize, and/or discomposethe encapsulant. Mechanical action may also be used sparingly to assistin the debonding process. For example, soft brushes may be used inconjunction with a solvent to remove encapsulant from the sliders sothat no residue is left behind.

Encapsulant Fluids and Debondable Encapsulants

The selection of encapsulant fluids and debondable encapsulantsrepresents a particularly important aspect of the invention. Asdiscussed above, the encapsulant fluids are selected for their abilityto gap-fill and to form slider arrays having high planarization values.However, encapsulant fluids having a desirable gap-filling capabilitytend to form encapsulants having poor debonding performance. Thus, whilea number of encapsulant materials have been investigated, only arelative few have been found to exhibit both excellent gap-fillingcapabilities and bonding/debonding performance.

For example, a number of thermosetting materials satisfy certainprocessing and solvent resistance requirements of the invention. Epoxieshaving acceptable gap-filling capabilities and suitable forsemiconductor packaging applications may be adapted for use inconjunction with the invention. These epoxies are commercially availablefrom a number of sources, e.g., under the trademark Epotek® from EpoxyTechnology (Billerica, Mass.). Nevertheless, commercial thermosettingmaterials are typically formulated to form permanent rather thantemporary bonds. As a result, when used in conjunction with the presentinvention, encapsulants formed from such thermosetting materials are noteasily removable and unsuited for the invention.

It has also been observed that thermoplastics, as a general class ofmaterials, are readily removed from sliders of slider assemblies.However, encapsulant fluids containing thermoplastics typically includea solvent to lower the viscosity of the thermoplastic to a degreesufficient to effect gap filling. Thus, thermoplastic systems typicallyexhibit several distinct disadvantages. For example, encapsulant fluidscan only be applied in a manner that allows the solvent to evaporatewithout leave voids or other inhomogeneities. In addition, encapsulantsformed from thermoplastics typically do not possess the requisiteresistance to fluids employed for lithographic patterning of anair-bearing surface of a slider.

Thus, the invention optional provides an encapsulant that has both athermoplastic polymer as well as a thermoset polymer, thereby meetingthe need for a material that can be deposited in liquid form without theassistance of a solvent. When a solventless encapsulant is formed,solvent which does not take part in the polymerization reaction isabsent from the components utilized to make the polymeric encapsulant.Accordingly, upon mixing the various components, e.g., the componentsthat contain the first and optional second monomers, there is generallyno solvent to be evaporated or entrapped into the resultingthermosetting polymeric materials. In other words, the whole system maybe 100% active, and no waste may occur as a result through solventevaporation. Under such solventless conditions, encapsulants formed aregenerally void free, since there are no solvent losses throughevaporation or solvent entrapments to cause porosity and blistering. Asan added benefit, the absence of solvents eliminates environmentalpollution caused by solvent loss.

The inventive encapsulants may be formed through a polymerizationmechanism that involves the reaction of the first constituent,generally, but not necessarily through addition polymerixation withoutthe formation of any volatile by-products which could cause voids,blisters or entrapments. In some instances, these polymers can includeladder-like type polymers wherein the components are cross-linkedspacially in the form of a ladder. For example, two linear parallelpolymeric chains are intersected at their repeated reaction sites bycomponents which form the steps of the spacial ladder. To effect desiredcuring, heat may be required, e.g., to a temperature of about 60° C. toabout 150° C., or more typically, of about about 80° C. to about 120° C.from for about 1.5 hours. Heating time may be shortened at higher curingtemperatures. The desired shelf-life for the inventive encapsulant fluidis at least about 30 minutes, preferably at least about an hour. Thatis, the first constituent preferably has a low viscosity at roomtemperature for at least the duration of the desired shelflife.

In some instances, the first encapsulant polymer may be formed from anamine and an acrylate or epoxide group. For example, an amine-containingmonomer may comprise mono, di, tri, tetra or poly amines,amine-terminated structures or an adduct of mono, di, tri, orpolyamines. The additional monomer may comprise mono, di orpolyacrylates, mixtures of mono, di or polyacrylates, or a mixture ofmono, di or poly acrylates and mono, di or polyfunctional epoxidesand/or glycidyl esters of acrylic acid or methacrylic acid.

Examplary mono amines include ethanol amine, 2 ethyl-hexyl amine, nonylamine, hexadecyl amine, and octadecyl amine. Useful diamines include,but are not limited to, hydrazine, ethylene diamine, 1,4-butylenediamine, 1,6-hexamethylene diamine, 1,2-cyclohexamethylene diamine. Tri(or poly)amines suitable for the invention include, without limitation,diethylene triamine, dipropylene triamine, triethylene tetramine,tetraethylene pentamine, and bis hexamethylene triamine.

Mono, di or poly functional acrylates useful in this invention include,for example, those having aliphatic, cycloaliphatic, or aromaticstructures and their combinations. Illustrative examples of monofunctional acrylics are: acrylonitrile, methyl acrylonitrile,acrylamide, methyl acrylamide, N-methylol acrylamide, N-methylol methylacrylamide, N,N′ dimethylol acrylamide, N,N′ dimethylol methylacrylamide, diacetone acrylamide, diacetone methyl acrylamide, hydroxylethyl acrylate, hydroxyl propyl acrylate. Illustrative examples ofdifunctional acrylates are the diacrylates and dimethyl acrylates of 1,4butylene diol, neopentyl glycol, oxodiethylene glycol, oxotriethyleneglycol, oxotetraethylene glycol, and oxo polyethyleneglycols.Illustrative examples of tri (or poly) functional acrylates include,without limitation triesters of acrylic acid, or methyl acrylic acid,with trimethylol ethane, trimethylol propane, and pentaerythritol.

Illustrative examples of mono, di or poly functional epoxides includeethylene oxide, propylene oxide, butylene oxide, and styrene oxides.

In instances that involve in situ polymerization via reaction of aplurality of moieties, e.g., from amines and epoxides, the moieties aretypically present in a stoichiometric ratio. Alternatively,nonstoichometric ratios may be involved. In particular, commerciallyavailable thermosetting resins under the trademark Epotek® from EpoxyTechnology (Billerica, Mass.) may be used to yield a transparentmaterial, which had a prepolymerization a viscosity similar to that ofwater. Once subjected to a temperature of 90° C. over a 1.5 hour period,the low viscosity monomer mixture may exhibit a desired dimensionalstability, and solvent resistance. Moreover, the polymer formed may bereadily removed by the appropriate solvent choice, e.g., propyleneglycol methyl ether acetate and N-methylpyrrolidinone.

In addition, the first polymer may be formed from moiteies other thanepoxides and amines. Acrylates and/or carboxylic acids, and anhydridesmay be used as well. Exemplary reactions adaptable for use with theinvention are known in the art and are described in U.S. Pat. No.4,051,195 to McWhorter, U.S. Pat. No. 4,675,374 Nichols, and U.S. Pat.No. 4,742,147 to Nichols.

As discussed above, the second consitutent may be comprised of a secondpolymer or a second monomer suitable for polymerication to form thesecond polymer, as long as the second polymer is different from thefirst. Thus, for example, when the first polymer is formed from anepoxide and an amine, the second polymer is typically not formed from anepoxide and an amine. Nevertheless, the second polymer may be formedfrom an epoxide and amine combination that is different from the epoxideand combination for the first polymer. In such a case, the first andsecond constituents of the encapsulant fluid may not substantially reactwith reach other.

When the second constituent is comprised of a second monomer suitablefor in situ polymerization, the first and second polymers may bepolymerized via different mechanisms. For example, the first polymer maybe polymerized via condensation, e.g., reaction between an amine and anepoxide, and the second polymer may be polymerized via addition, e.g.,addition polymerization of an acrylate.

In addition, different types of polymeric structures may be employed,for the first and the second polymer. For example, the first polymer maybe comprised of a linear polymer, a branch polymer, or a networkpolymer. The second polymer may be comprised of a linear polymer. Insome instances, the first and second polymers may form aninterpenetrating network. Depending on the microstructure of theencapsulant, e.g., crystallinity, crystal size, etc., the encapsulantmay be transparent.

It should be noted that the bonding and debonding performance of anencapsulant is dependent on a variety of factors and is not generallypredictable solely based on the presence of a plurality of differentpolymers or the presence of a polymer that is formed in situ. Thus, forexample, while the presence of certain polymers formed in situ may allowthe encapsulant to exhibit acceptable bonding and debonding performance,other polymers formed in situ may not. Thus, when a class of polymers isgenerally identified as exhibiting acceptable bonding/debondingperformance, specific polymers within that class which suffer from poorbonding and/or debonding performance is specifically excluded by theinvention.

It has been experimentally verified that an encapsulant may be formedvia concurrent polymerization of a linear polymer (from liquid monomericacrylates and a dissolved free radical initiator that decomposes atabout 60° C. to 70° C.) and a thermosetting polymer (from diepoxide witha stoichiometric quantity of tetraamine). The ingredients formed ahomogeneous mixture in the same “pot.” Once heated to 90° C. for 1.5hours, homogeneous transparent encapsulant was formed with excellentstep heights, solvent resistance to lithographic steps, anddebondability.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof, theforegoing description is intended to illustrate and not limit the scopeof the invention. Other aspects, advantages and modifications will beapparent to those skilled in the art to which the invention pertains.

All patents and publications cited herein are incorporated by referencein their entireties.

1. A slider assembly comprising a plurality of sliders bonded by a soliddebondable encapsulant comprising different first and second polymerssuch that each slider has an encapsulant-free surface, theencapsulant-free surfaces are coplanar to each other, and theencapsulant is formed via in situ polymerization of an encapsulantfluid, wherein the encapsulant fluid is comprised of a homogeneousmixture of first and second constituents, the first constituent iscomprised of a first monomer suitable for in situ polymerization to formthe first polymer, the second constituent is comprised of the secondpolymer or a second monomer suitable for in situ polymerization to formthe second polymer, and the first constituent does not substantiallyreact with the second constituent.
 2. The slider assembly of claim 1,wherein the first constituent is comprised of an amine and an epoxide.3. The slider assembly of claim 2, wherein the epoxide is a diepoxide.4. The slider assembly of claim 2, wherein the amine is a tetraamine. 5.The slider assembly of claim 2, wherein the amine and the epoxide arepresent in a stoichiometric ratio.
 6. The slider assembly of claim 1,wherein the first monomer is comprised of an acrylate.
 7. The sliderassembly of claim 1, wherein the first polymer is a thermosettingpolymer and the second polymer is a thermoplastic polymer.
 8. The sliderassembly of claim 1, wherein the second constituent is comprised of thesecond monomer suitable for in situ polymerization.
 9. The sliderassembly of claim 8, wherein the first and second polymers arepolymerized via different mechanisms.
 10. The slider assembly of claim9, wherein the first polymer is polymerized via condensation and thesecond polymer is polymerized via addition.
 11. The slider assembly ofclaim 10, wherein the first constituent is comprised of an amine and anepoxide and the second constituent is comprised of an acrylate.
 12. Theslider assembly of claim 1, wherein the first polymer is comprised of alinear polymer.
 13. The slider assembly of claim 1, wherein the firstpolymer is comprised of a branch polymer.
 14. The slider assembly ofclaim 1, wherein the first polymer is comprised of a network polymer.15. The slider assembly of claim 13, wherein the second polymer iscomprised of a linear polymer.
 16. The slider assembly of claim 14,wherein the second polymer is comprised of a linear polymer.
 17. Theslider assembly of claim 1, wherein the encapsulant is transparent. 18.The slider assembly of claim 1, having a contiguous planar surfacecomprised of at least one encapsulant region and containing the coplanarslider surfaces.
 19. The slider assembly of claim 18, wherein thesliders are arranged in an array.
 20. The slider assembly of claim 19,wherein the array is a rectilinear array.
 21. The slider assembly ofclaim 20, wherein the sliders do not contact each other.
 22. The sliderassembly of claim 20, wherein the coplanar surfaces of the sliders areeach an air-bearing surface.
 23. The slider assembly of claim 22,further comprising a substrate in contact with the air-bearing surfaces.24. The slider assembly of claim 23, wherein the substrate is comprisedof a laminate of a flexible tape and an adhesive, wherein the adhesiveis in contact with the air-bearing surfaces.
 25. The slider assembly ofclaim 24, wherein the adhesive is a pressure sensitive adhesive.
 26. Theslider assembly of claim 24, wherein the adhesive preferentially adheresto the tape over the air-bearing surfaces.
 27. The slider assembly ofclaim 20, further comprising a carrier attached to the encapsulant, atleast one slider, or both, wherein the carrier does not cover any of thecoplanar slider surfaces.
 28. The slider assembly of claim 22, furthercomprising a resist layer on the air-bearing surfaces, wherein theencapsulant is mechanically stable upon exposure to the resist layer orany component thereof.
 29. The slider assembly of claim 28, wherein theencapsulant is subject to solvation by a solvent not found in the resistlayer.
 30. A method for forming a slider assembly, comprising: (a)arranging a plurality of sliders each having a surface such that thesurfaces are coplanar to each other; (b) dispensing an encapsulant fluidto bond the sliders without contacting the coplanar slider surfaces,wherein the encapsulant fluid is comprised of a homogeneous mixture offirst and second constituents, the first constituent is comprised of afirst monomer suitable for in situ polymerization to form a firstpolymer, the second constituent is comprised of a second polymer that isdifferent from the first polymer or a second monomer suitable for insitu polymerization to form the second polymer, and the firstconstituent does not substantially react with the second constituent;and (c) effecting in situ polymerization of the encapsulant fluid so asto form a solid debondable polymeric encapsulant comprised of the firstand second polymers.
 31. The method of claim 30, wherein the secondconstituent is comprised of the second monomer suitable for in situpolymerization.
 32. The method of claim 31, wherein step the first andsecond monomers are simultaneously polymerized in situ during step (c).33. The method of claim 30, wherein step (c) is carried out in atemperature range of about 60° C. to about 150° C.
 34. The method ofclaim 33, wherein step (c) is carried out in a temperature range ofabout 80° C. to about 120° C.
 35. The method of claim 30, wherein theencapsulant fluid dispensed in step (b) does not contain any solvent.36. The method of claim 30, wherein step (a) comprises placing thesliders on a laminate of a flexible tape and an adhesive such thatslider surfaces contact the adhesive.
 37. The method of claim 36,wherein the adhesive is resistant or impervious to solvation by theencapsulant fluid.
 38. The method of claim 30, wherein the fluid mixturehas an initial viscosity of no more than about 800 centistokes.
 39. Themethod of claim 30, wherein the initial viscosity is no more than about500 centistokes.
 40. A method for patterning an air-bearing surface of aslider, comprising: (a) applying a resist layer on an air-bearingsurface of a slider, wherein at least a portion of the slider other thanthe air-bearing surface is encapsulated in a debondable solidencapsulant comprised of different first and second polymers formed viain situ polymerization of an encapsulant fluid, wherein the encapsulantfluid is comprised of a homogeneous mixture of first and secondconstituents, the first constituent is comprised of a first monomersuitable for in situ polymerization to form the first polymer, thesecond constituent is comprised of the second polymer or a secondmonomer suitable for in situ polymerization to form the second polymer,and the first constituent does not substantially react with the secondconstituent; (b) removing a portion of the resist layer to uncover aportion of the air-bearing surface in a patternwise manner; and (c)adding material to and/or removing material from the uncovered portionof the air-bearing surface, thereby patterning the air-bearing surfaceof the slider, wherein the encapsulant is mechanically stable uponexposure to any fluid employed in steps (a), (b), and/or (c).
 41. Themethod of claim 40, further comprising, after step (a) and before step(b), exposing the resist layer to photons in the patternwise manner.